DRAM circuit. Image: Dick Thomas Johnson/Flickr
The great thing about DRAM is we can pack millions of these capacitors on the surface of a chip, in a grid pattern of rows and columns. In most cases the more capacitors a chip has, the faster your CPU can processes operations, but the density of these capacitors poses a problem. The electrical charge of a single capacitor can leak out and affect the charge of its neighbors, changing the binary value of nearby capacitors and and corrupting a computer's memory in the process. To solve this, a dedicated tool called a memory controller refreshes the charge on the capacitors thousands of times a second to ensure bit values stay correct.
It's like breaking into an apartment by repeatedly slamming a neighbor's door until the vibrations open the door you were after